Enforce stricter linting across the entire codebase, covering both TypeScript and Python files.

[Darshan808]

Fixes #80

Description

• Upgrade to ESLint v9
• Resolve all linting issues in TypeScript files
• Enabled "ALL" ruff rules and used an AI agent (Claude Code with Sonnet 4.6) to fix ~500 lint errors across python files.

[Darshan808]

Used an AI agent to resolve the Ruff lint errors; it handled most cases well.

[krassowski]

I would disable FBT001 it is just not practical here since we need to maintain compatibility, and it appears everywhere now

[krassowski]

Looks good to my human eye, I will ask copilot for a pass

[Copilot]

Pull request overview

This PR tightens linting across the repository by upgrading the JavaScript/TypeScript linting stack to ESLint v9 (flat config) and by enabling Ruff’s full rule set for Python, with targeted per-file ignores to keep third-party/legacy code workable.

Changes:

• Upgrade ESLint to v9, migrate from package.json eslint config to eslint.config.mjs, and update TypeScript lint dependencies.
• Enable ruff rule selection "ALL" and add/adjust per-file ignores for the semver port.
• Apply widespread typing/cleanup refactors across TS and Python code to satisfy stricter lint rules.

Reviewed changes

Copilot reviewed 25 out of 26 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
yarn.lock	Updates JS tooling dependency graph for ESLint v9 / typescript-eslint / related packages.
package.json	Switches lint dependencies to ESLint v9 + flat-config ecosystem and removes inline eslint config.
eslint.config.mjs	Adds ESLint flat config with TS + Prettier integration and global ignores.
src/webpack.config.base.ts	Tightens types for SVG data URL generator callback.
src/webpack-plugins.ts	Replaces any usage with rspack types and tightens watch filesystem wrapper typing.
src/extensionConfig.ts	Improves typing for shared deps/config generation and rspack plugin/rules definitions.
src/build.ts	Minor TS cleanup/typing changes (e.g., avoid unused destructured vars; tighten SVG generator types).
src/build-labextension.ts	Improves callback typings and error handling types around rspack compiler output.
pyproject.toml	Enables Ruff select = ["ALL"] and expands per-file ignores for the semver port.
.pre-commit-config.yaml	Adjusts ruff hooks configuration (notably adds exclude: tests).
.licenserc.yaml	Exempts the semver port file from license header enforcement.
jupyter_builder/yarn.js	Removes eslint-disable header from bundled yarn script (generated file).
jupyter_builder/main.py	Adds module docstring and tightens typing/docstrings.
jupyter_builder/jlpm.py	Adds typing, pathlib usage, and docstring improvements.
jupyter_builder/jupyterlab_semver.py	Large Ruff-driven cleanup: typing, docstrings, small refactors, and regex flag constants.
jupyter_builder/federated_extensions.py	Broad pathlib + typing refactor for extension build/develop/watch utilities.
jupyter_builder/federated_extensions_requirements.py	Moves to pathlib globs and typing cleanups.
jupyter_builder/extension_commands/*	Adds docstrings, typing, and pathlib usage in CLI command apps.
jupyter_builder/base_extension_app.py	Typing/docstring improvements and pathlib-based HERE.
jupyter_builder/debug_log_file_mixin.py	Typing improvements and pathlib usage for log file handling.
jupyter_builder/core_path.py	Docstring formatting and signature formatting tweaks.
jupyter_builder/commands.py	Adds typing and minor refactors to overlap comparison helpers.
jupyter_builder/__init__.py / jupyter_builder/extension_commands/__init__.py	Adds module docstrings.

Comments suppressed due to low confidence (1)

src/extensionConfig.ts:31

• IOptions still exposes watchMode?: boolean, but generateConfig no longer reads or applies it (it’s not referenced anywhere in the file). This makes the option a no-op and can confuse downstream callers; either remove it from IOptions or reintroduce handling so it affects the generated rspack configuration.

export interface IOptions {
  packagePath?: string;
  corePackageFile?: string;
  staticUrl?: string;
  mode?: 'development' | 'production';
  devtool?: string;
  watchMode?: boolean;
}

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[Darshan808]

Could you ask copilot for one more pass?

[krassowski]

Also needs resolving conflicts due to rspack 2 merge

[Copilot]

Pull request overview

Copilot reviewed 25 out of 26 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 28 out of 29 changed files in this pull request and generated 3 comments.

[krassowski]

In general, changes in semver file are why I went for another round of copilot. These are hard to reason about and there are no unit tests for that functionality. I worry that we could break some version checking here due to subtle differences in logic flow. Could you revert the more involved changes (typing additions are fine) and just add comments asking linter to ignore specific lines in that file?

[Darshan808]

The semver file’s original source has also remained unchanged for the past 9 years. Given that, I agree it’s probably safer to ignore the mypy errors here rather than risk introducing subtle logic regressions.

[krassowski]

Thank you!